memcmp.S revision 1.5.16.2
1 /* $NetBSD: memcmp.S,v 1.5.16.2 2020/04/21 19:37:42 martin Exp $ */ 2 3 /* 4 * Copyright 2003 Wasabi Systems, Inc. 5 * All rights reserved. 6 * 7 * Written by Steve C. Woodford for Wasabi Systems, Inc. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. All advertising materials mentioning features or use of this software 18 * must display the following acknowledgement: 19 * This product includes software developed for the NetBSD Project by 20 * Wasabi Systems, Inc. 21 * 4. The name of Wasabi Systems, Inc. may not be used to endorse 22 * or promote products derived from this software without specific prior 23 * written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND 26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 27 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 28 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL WASABI SYSTEMS, INC 29 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 30 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 31 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 32 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 33 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 34 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 35 * POSSIBILITY OF SUCH DAMAGE. 36 */ 37 /* 38 * Copyright (c) 2002 ARM Ltd 39 * All rights reserved. 40 * 41 * Redistribution and use in source and binary forms, with or without 42 * modification, are permitted provided that the following conditions 43 * are met: 44 * 1. Redistributions of source code must retain the above copyright 45 * notice, this list of conditions and the following disclaimer. 46 * 2. Redistributions in binary form must reproduce the above copyright 47 * notice, this list of conditions and the following disclaimer in the 48 * documentation and/or other materials provided with the distribution. 49 * 3. The name of the company may not be used to endorse or promote 50 * products derived from this software without specific prior written 51 * permission. 52 * 53 * THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED 54 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 55 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 56 * IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 57 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED 58 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 59 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 60 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 61 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 62 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 63 */ 64 65 #include <machine/asm.h> 66 67 RCSID("$NetBSD: memcmp.S,v 1.5.16.2 2020/04/21 19:37:42 martin Exp $") 68 69 ENTRY(memcmp) 70 mov ip, r0 71 #if defined(_KERNEL) && !defined(_STANDALONE) 72 cmp r2, #0x06 73 beq .Lmemcmp_6bytes 74 #endif 75 mov r0, #0x00 76 77 /* Are both addresses aligned the same way? */ 78 cmp r2, #0x00 79 eorsne r3, ip, r1 80 RETc(eq) /* len == 0, or same addresses! */ 81 tst r3, #0x03 82 subne r2, r2, #0x01 83 bne .Lmemcmp_bytewise2 /* Badly aligned. Do it the slow way */ 84 85 /* Word-align the addresses, if necessary */ 86 sub r3, r1, #0x05 87 ands r3, r3, #0x03 88 add r3, r3, r3, lsl #1 89 addne pc, pc, r3, lsl #3 90 nop 91 92 /* Compare up to 3 bytes */ 93 ldrb r0, [ip], #0x01 94 ldrb r3, [r1], #0x01 95 subs r0, r0, r3 96 RETc(ne) 97 subs r2, r2, #0x01 98 RETc(eq) 99 100 /* Compare up to 2 bytes */ 101 ldrb r0, [ip], #0x01 102 ldrb r3, [r1], #0x01 103 subs r0, r0, r3 104 RETc(ne) 105 subs r2, r2, #0x01 106 RETc(eq) 107 108 /* Compare 1 byte */ 109 ldrb r0, [ip], #0x01 110 ldrb r3, [r1], #0x01 111 subs r0, r0, r3 112 RETc(ne) 113 subs r2, r2, #0x01 114 RETc(eq) 115 116 /* Compare 4 bytes at a time, if possible */ 117 subs r2, r2, #0x04 118 bcc .Lmemcmp_bytewise 119 .Lmemcmp_word_aligned: 120 ldr r0, [ip], #0x04 121 ldr r3, [r1], #0x04 122 subs r2, r2, #0x04 123 cmpcs r0, r3 124 beq .Lmemcmp_word_aligned 125 sub r0, r0, r3 126 127 /* Correct for extra subtraction, and check if done */ 128 adds r2, r2, #0x04 129 cmpeq r0, #0x00 /* If done, did all bytes match? */ 130 RETc(eq) /* Yup. Just return */ 131 132 /* Re-do the final word byte-wise */ 133 sub ip, ip, #0x04 134 sub r1, r1, #0x04 135 136 .Lmemcmp_bytewise: 137 add r2, r2, #0x03 138 .Lmemcmp_bytewise2: 139 ldrb r0, [ip], #0x01 140 ldrb r3, [r1], #0x01 141 subs r2, r2, #0x01 142 cmpcs r0, r3 143 beq .Lmemcmp_bytewise2 144 sub r0, r0, r3 145 RET 146 147 #if defined(_KERNEL) && !defined(_STANDALONE) 148 /* 149 * 6 byte compares are very common, thanks to the network stack. 150 * This code is hand-scheduled to reduce the number of stalls for 151 * load results. Everything else being equal, this will be ~32% 152 * faster than a byte-wise memcmp. 153 */ 154 .align 5 155 .Lmemcmp_6bytes: 156 ldrb r3, [r1, #0x00] /* r3 = b2#0 */ 157 ldrb r0, [ip, #0x00] /* r0 = b1#0 */ 158 ldrb r2, [r1, #0x01] /* r2 = b2#1 */ 159 subs r0, r0, r3 /* r0 = b1#0 - b2#0 */ 160 ldrbeq r3, [ip, #0x01] /* r3 = b1#1 */ 161 RETc(ne) /* Return if mismatch on #0 */ 162 subs r0, r3, r2 /* r0 = b1#1 - b2#1 */ 163 ldrbeq r3, [r1, #0x02] /* r3 = b2#2 */ 164 ldrbeq r0, [ip, #0x02] /* r0 = b1#2 */ 165 RETc(ne) /* Return if mismatch on #1 */ 166 ldrb r2, [r1, #0x03] /* r2 = b2#3 */ 167 subs r0, r0, r3 /* r0 = b1#2 - b2#2 */ 168 ldrbeq r3, [ip, #0x03] /* r3 = b1#3 */ 169 RETc(ne) /* Return if mismatch on #2 */ 170 subs r0, r3, r2 /* r0 = b1#3 - b2#3 */ 171 ldrbeq r3, [r1, #0x04] /* r3 = b2#4 */ 172 ldrbeq r0, [ip, #0x04] /* r0 = b1#4 */ 173 RETc(ne) /* Return if mismatch on #3 */ 174 ldrb r2, [r1, #0x05] /* r2 = b2#5 */ 175 subs r0, r0, r3 /* r0 = b1#4 - b2#4 */ 176 ldrbeq r3, [ip, #0x05] /* r3 = b1#5 */ 177 RETc(ne) /* Return if mismatch on #4 */ 178 sub r0, r3, r2 /* r0 = b1#5 - b2#5 */ 179 RET 180 #endif 181 END(memcmp) 182 183 #if defined(__ARM_EABI__) && !defined(_RUMPKERNEL) 184 STRONG_ALIAS(__aeabi_memcmp, memcmp) 185 #endif 186
Indexes created Wed Oct 22 13:09:56 GMT 2025